/in/foo.cc: In function 'int main()':
/in/foo.cc:5:13: error: 'k' was not declared in this scope
  double x,a=k*b+r,b;
             ^
/in/foo.cc:5:15: error: 'b' was not declared in this scope
  double x,a=k*b+r,b;
               ^
/in/foo.cc:5:17: error: 'r' was not declared in this scope
  double x,a=k*b+r,b;
                 ^
/in/foo.cc:5:11: warning: unused variable 'a' [-Wunused-variable]
  double x,a=k*b+r,b;
           ^